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Lu, WT; Sridhar, S

Electronic structure: Wide-band, narrow-band, and strongly correlated systems-Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction Journal Article

In: Physical Review B Condensed Matter And Materials Physics, vol. 78, no. 23, pp. 233101, 2008.

@article{lu2008electronic,

title = {Electronic structure: Wide-band, narrow-band, and strongly correlated systems-Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction},

author = {WT Lu and S Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Physical Review B Condensed Matter And Materials Physics},

volume = {78},

number = {23},

pages = {233101},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Lu, WT; Sridhar, S

Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction Journal Article

In: Physical Review B, vol. 77, no. 23, pp. 233101, 2008.

@article{lu2008superlens,

title = {Superlens imaging theory for anisotropic nanostructured metamaterials with broadband all-angle negative refraction},

author = {WT Lu and S Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Physical Review B},

volume = {77},

number = {23},

pages = {233101},

publisher = {APS},

abstract = {We show that a metamaterial consisting of aligned metallic nanowires in a dielectric matrix has strongly anisotropic optical properties. For long wavelngths, the longitudinal SPR, the material exhibits positive transverse permittivity and negative longitudinal permittivity, relative to the nanowires axis, enabling the achievement of broadband all-angle negative refraction and superlens imaging. An imaging theory of superlens made of these media is established. High performance systems made with Au, Ag, or Al nanowires in nanoporous templates are designed and predicted to work from the infrared up to ultraviolet frequencies.

},

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tppubtype = {article}

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Banyal, Ravinder; Casse, BDF; Lu, WT; Huang, YJ; Selvarasah, S; Dokmeci, M; Perry, CH; Sridhar, S

Experimental realization of a generalized superlens using negative refraction at infrared wavelengths Inproceedings

In: APS Meeting Abstracts, 2008.

@inproceedings{banyal2008experimental,

title = {Experimental realization of a generalized superlens using negative refraction at infrared wavelengths},

author = {Ravinder Banyal and BDF Casse and WT Lu and YJ Huang and S Selvarasah and M Dokmeci and CH Perry and S Sridhar},

year = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We demonstrate experimentally using a near-field scanning optical microscope the imaging of a point source by a generalized superlens fabricated in InGaAsP/InP heterostructure at wavelengths around lambda= 1.5 mum. The theory of superlens imaging with lens equation u+ v= sigmad gives excellent explanation of wave refraction and imaging formation of our superlens with an effective lens property ε eff= 0.43. This can be used as the basis for design optical elements made of photonic crystals.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

Lu, WT; Zhang, S; Huang, YJ; Sridhar, S

Effective medium theory of photonic crystals Inproceedings

In: APS Meeting Abstracts, 2008.

@inproceedings{lu2008effective,

title = {Effective medium theory of photonic crystals},

author = {WT Lu and S Zhang and YJ Huang and S Sridhar},

year = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We develop an effective medium theory for photonic crystals including negative index metamaterials. This theory is based on field summation within the unit cell. The unit cell is determined by the surface termination. The orientation of the surface breaks the field summation symmetry. This theory is self-consistent. The effective permittivity and permeability tensors will give the exact dispersion relation obtained from the band structure calculation. For waves incident into multilayered structures, our theory gives exact transmittance and reflectance for any wavelengths. For interface with periodic surface structures, our theory gives very accurate results for wavelength down to being comparable with the lattice spacing. By properly taking into account the multiple Bloch modes inside the photonic crystal, our theory can be made to give exact Bragg coefficients.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

Huang, YJ; Lu, WT; Sridhar, S

Nanowire waveguide made from extremely anisotropic metamaterials Journal Article

In: Physical Review A, vol. 77, no. 6, pp. 063836, 2008.

@article{huang2008nanowire,

title = {Nanowire waveguide made from extremely anisotropic metamaterials},

author = {YJ Huang and WT Lu and S Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Physical Review A},

volume = {77},

number = {6},

pages = {063836},

publisher = {APS},

abstract = {Exact solutions are obtained for all the modes of wave propagation along an anisotropic cylindrical waveguide. Closed-form expressions for the energy flow on the waveguide are also derived. For extremely anisotropic waveguide where the transverse permittivity is negative while the longitudinal permittivity is positive, only transverse magnetic (TM) and hybrid modes will propagate on the waveguide. At any given frequency the waveguide supports an infinite number of eigenmodes. Among the TM modes, at most only one mode is forward wave. The rest of them are backward waves which can have very large effective index. At a critical radius, the waveguide supports degenerate forward- and backward-wave modes with zero group velocity. These waveguides can be used as phase shifters and filters, and as optical buffers to slow down and trap light.

},

keywords = {},

pubstate = {published},

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}

Menon, L; Lu, WT; Friedman, AL; Bennett, SP; Heiman, D; Sridhar, S

Negative index metamaterials based on metal-dielectric nanocomposites for imaging applications Journal Article

In: Applied Physics Letters, vol. 93, no. 12, pp. 123117, 2008.

@article{menon2008negative,

title = {Negative index metamaterials based on metal-dielectric nanocomposites for imaging applications},

author = {L Menon and WT Lu and AL Friedman and SP Bennett and D Heiman and S Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {93},

number = {12},

pages = {123117},

publisher = {American Institute of Physics},

abstract = {Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.},

keywords = {},

pubstate = {published},

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}

Menon, Latika; Lu, Wentao; Friedman, Adam; Bennett, Steven; Heiman, Donald; Sridhar, Srinivas

Negative Index Metamaterials for Superlenses Based on Metal-Dielectric Nanocomposites Inproceedings

In: APS Meeting Abstracts, 2008.

@inproceedings{menon2008negativeb,

title = {Negative Index Metamaterials for Superlenses Based on Metal-Dielectric Nanocomposites},

author = {Latika Menon and Wentao Lu and Adam Friedman and Steven Bennett and Donald Heiman and Srinivas Sridhar},

year = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites. The nanocomposites are prepared using a versatile bottom-up nanofabrication approach involving the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Aluminum oxide nanotemplates with specific pore dimensions are fabricated by means of electrochemical anodization. Following this, Au/Ag nanowires with specific wire dimensions are electrodeposited inside the pores. Optical absorbance measurements show resonance peaks corresponding to transverse and longitudinal surface plasmon modes. Peak position and intensity are found to be strongly dependent on nanocomposite dimensions, filling factor (ratio of the volume of metal versus the volume of dielectric) and angle of incidence with respect to the wire axis. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for superlens imaging.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

Casse, BDF; Lu, WT; Huang, YJ; Sridhar, S

Nano-optical microlens with ultrashort focal length using negative refraction Journal Article

In: Applied Physics Letters, vol. 93, no. 5, pp. 053111, 2008.

@article{casse2008nano,

title = {Nano-optical microlens with ultrashort focal length using negative refraction},

author = {BDF Casse and WT Lu and YJ Huang and S Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {93},

number = {5},

pages = {053111},

publisher = {American Institute of Physics},

abstract = {We have experimentally realized an ultrashort focal length planoconcave microlens in an InP/InGaAsP semiconductor two-dimensional photonic crystal with negative index of refraction n = -0.7. At wavelength 1.5 microns, the lens exhibits ultrashort focal lengths of 12 microns (~ 8x wanelength) and numerical aperture close to unity. The focused beam has a near diffraction-limited spot size of 1.05 microns (~ 0.68 wavelength) at full width at half maximum. The negative refractive index and focusing properties of the microlens are confirmed by 2D finite-difference time-domain simulations. Such ultrarefractive negative-index nano-optical microlenses can be integrated into existing emiconductor heterostructure platforms for next-generation optoelectronic applications.

},

keywords = {},

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Gultepe, Evin; Nagesha, Dattatri; Casse, Bernard Didier Frederic; Selvarasah, Selvapraba; Busnaina, Ahmed; Sridhar, Srinivas

Large scale 3D vertical assembly of single-wall carbon nanotubes at ambient temperatures Journal Article

In: Nanotechnology, vol. 19, no. 45, pp. 455309, 2008.

@article{gultepe2008large,

title = {Large scale 3D vertical assembly of single-wall carbon nanotubes at ambient temperatures},

author = {Evin Gultepe and Dattatri Nagesha and Bernard Didier Frederic Casse and Selvapraba Selvarasah and Ahmed Busnaina and Srinivas Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Nanotechnology},

volume = {19},

number = {45},

pages = {455309},

publisher = {IOP Publishing},

abstract = {We demonstrate three-dimensional directed assembly of single-wall carbon nanotubes (SWNT) into porous alumina nanotemplates on silicon substrates by means of electrophoresis and dielectrophoresis at ambient temperatures. Assembled SWNT provided an interconnection between the surface and base of the nanotemplate. I–V measurements clearly show that the connection between silicon and SWNT is established inside the templates. This technique is particularly useful for large scale, rapid, 3D assembly of SWNT over centimeter square areas under mild conditions for nanoscale electronics applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Casse, Bernard Didier F; Banyal, Ravinder K; Lu, WT; Huang, YJ; Selvarasah, Selvapraba; Dokmeci, M; Sridhar, Srinivas

Nanoengineering of a negative-index binary-staircase lens for the optics regime Journal Article

In: Applied Physics Letters, vol. 92, no. 24, pp. 243122, 2008.

@article{casse2008nanoengineering,

title = {Nanoengineering of a negative-index binary-staircase lens for the optics regime},

author = {Bernard Didier F Casse and Ravinder K Banyal and WT Lu and YJ Huang and Selvapraba Selvarasah and M Dokmeci and Srinivas Sridhar},

year = {2008},

date = {2008-01-01},

journal = {Applied Physics Letters},

volume = {92},

number = {24},

pages = {243122},

publisher = {American Institute of Physics},

abstract = {We show that a binary-staircase optical element can be engineered to exhibit an effective negative index of refraction, thereby expanding the range of optical properties theoretically available for future optoelectronic devices. The mechanism for achieving a negative-index lens is based on exploiting the periodicity of the surface corrugation. By designing and nanofabricating a planoconcave binary-staircase lens in the InP/InGaAsP platform, we have experimentally demonstrated at 1.55 micrometers that such negative-index concave lenses can focus plane waves. The beam propagation in the lens was studied experimentally and was in excellent agreement with the three-dimensional finite-difference time-domain numerical simulations.

},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Lu, Wentao; Sridhar, Srinivas

Anisotropic nanostructured metamaterials for broadband all-angle negative refractionand flat lens imaging Inproceedings

In: APS Meeting Abstracts, 2008.

@inproceedings{lu2008anisotropic,

title = {Anisotropic nanostructured metamaterials for broadband all-angle negative refractionand flat lens imaging},

author = {Wentao Lu and Srinivas Sridhar},

year = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We show that a metamaterial consisting of aligned metallic nanowires in a dielectric matrix has strongly anisotropic optical properties. For filling ratio f< 1/2, the composite medium shows two surface plasmon resonances (SPRs): the transverse and longitudinal SPR with wavelengths lambda t< lambda l. For lambda t> lambda l, the longitudinal SPR, the material exhibits Re ε//< 0, Re ε> 0, relative to the nanowires axis, enabling the achievement of broadband all-angle negative refraction and flat lens (superlens) imaging systems. High performance systems made with Au, Ag or Al nanowires in nanoporous templates are designed and predicted to work from the infrared up to ultraviolet frequencies.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

Huang, YJ; Lu, WT; Sridhar, S

Alternative approach to all-angle negative refraction in two-dimensional photonic crystals Journal Article

In: Physical Review A, vol. 76, no. 1, pp. 013824, 2007.

@article{huang2007alternative,

title = {Alternative approach to all-angle negative refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year = {2007},

date = {2007-01-01},

journal = {Physical Review A},

volume = {76},

number = {1},

pages = {013824},

publisher = {APS},

abstract = {We show that with an appropriate surface modification, a slab of photonic crystal can be made to allow wave transmission within the photonic band gap. Furthermore, negative refraction and all-angle negative refraction (AANR) can be achieved by this surface modification in frequency windows that were not realized before in two-dimensional photonic crystals [C. Luo et al., Phys. Rev. B 65, 201104 (2002)]. This approach to AANR leads to different applications in flat lens imaging. Previous flat lens using photonic crystals requires object-image distance u+ v less than or equal to the lens thickness d, u+ v∼ d. Our approach can be used to design a flat lens with u+ v= σ d with σ≫ 1, thus being able to image large and/or far away objects. Our results are confirmed by finite-difference time-domain simulations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Lu, WT; Huang, YJ; Vodo, P; Banyal, RK; Perry, CH; Sridhar, S

A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation Journal Article

In: Optics express, vol. 15, no. 15, pp. 9166–9175, 2007.

@article{lu2007new,

title = {A new mechanism for negative refraction and focusing using selective diffraction from surface corrugation},

author = {WT Lu and YJ Huang and P Vodo and RK Banyal and CH Perry and S Sridhar},

year = {2007},

date = {2007-01-01},

journal = {Optics express},

volume = {15},

number = {15},

pages = {9166--9175},

publisher = {Optical Society of America},

abstract = {Refraction at a smooth interface is accompanied by momentum transfer normal to the interface. We show that corrugating an initially smooth, totally reflecting, non-metallic interface provides a momentum kick parallel to the surface, which can be used to refract light negatively or positively. This new mechanism of negative refraction is demonstrated by visible light and microwave experiments on grisms (grating-prisms). Single-beam all-angle-negative-refraction is achieved by incorporating a surface grating on a flat multilayered material. This negative refraction mechanism is used to create a new optical device, a grating lens. A planoconcave grating lens is demonstrated to focus plane microwaves to a point image. These results show that customized surface engineering can be usedto achieve negative refraction even though the bulk material has positive refractive index. The surface periodicity provides a tunable parameter to control beam propagation leading to novel optical and microwave devices.

},

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pubstate = {published},

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Huang, YJ; Lu, WT; Sridhar, S

PART B-Quantum optics, physics of lasers, nonlinear optics, classical optics-Alternative approach to all-angle negative refraction in two-dimensional photonic crystals Journal Article

In: Physical Review-Section A-Atomic Molecular and Optical Physics, vol. 76, no. 1, pp. 13824–13824, 2007.

@article{huang2007part,

title = {PART B-Quantum optics, physics of lasers, nonlinear optics, classical optics-Alternative approach to all-angle negative refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year = {2007},

date = {2007-01-01},

journal = {Physical Review-Section A-Atomic Molecular and Optical Physics},

volume = {76},

number = {1},

pages = {13824--13824},

publisher = {New York, NY: Published by the American Physical Society through the~…},

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pubstate = {published},

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Banyal, Ravinder; Casse, BDF; Vodo, Plarenta; Lu, WT; Sridhar, Srinivas

Nanophotonic structures for Negative Refraction at NIR and VIS Journal Article

In: APS, pp. X38–007, 2007.

@article{banyal2007nanophotonic,

title = {Nanophotonic structures for Negative Refraction at NIR and VIS},

author = {Ravinder Banyal and BDF Casse and Plarenta Vodo and WT Lu and Srinivas Sridhar},

year = {2007},

date = {2007-01-01},

journal = {APS},

pages = {X38--007},

abstract = {Nanophotonic structures were fabricated for negative index refraction at NIR and VIS frequencies. Structures include prisms and flat lenses fabricated in Si using nanolithography. Refraction and imaging experiments were carried out at NIR and VIS. Natural divergence of laser beam, collimation and guiding of the light within the device structures are also discussed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Huang, YJ; Lu, WT; Sridhar, S

New approach to all-angle-negative-refraction in two-dimensional photonic crystals Journal Article

In: APS, pp. S38–002, 2007.

@article{huang2007new,

title = {New approach to all-angle-negative-refraction in two-dimensional photonic crystals},

author = {YJ Huang and WT Lu and S Sridhar},

year = {2007},

date = {2007-01-01},

journal = {APS},

pages = {S38--002},

abstract = {We show that with an appropriate surface modification, a slab of photonic crystal can be made to allow wave transmission within the photonic band gap. Furthermore, negative refraction and all-angle negative refraction _AANR_ can be achieved by this surface modification in frequency windows that were not realized before in two-dimensional photonic crystals _C. Luo et al., Phys. Rev. B 65, 201104 _2002__. This approach to AANR leads to different applications in flat lens imaging. Previous flat lens using photonic crystals requires object-image distance u + v less than or equal to the lens thickness d, u + v = σd. Our approach can be used to design a flat lens with large σ, thus being able to image large and/or far away objects. Our results are confirmed by finite-difference time-domain simulations.

},

keywords = {},

pubstate = {published},

tppubtype = {article}

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Lu, Wentao; Vodo, P; Sridhar, Srinivas

Negative Refraction in Photonic Crystals Incollection

In: Physics of Negative Refraction and Negative Index Materials, pp. 133–147, Springer, Berlin, Heidelberg, 2007.

@incollection{lu2007negative,

title = {Negative Refraction in Photonic Crystals},

author = {Wentao Lu and P Vodo and Srinivas Sridhar},

year = {2007},

date = {2007-01-01},

booktitle = {Physics of Negative Refraction and Negative Index Materials},

pages = {133--147},

publisher = {Springer, Berlin, Heidelberg},

abstract = {An intriguing property of the left-handed material is negative refraction. The optical properties of materials that are transparent to electromagnetic (EM) waves can be characterized by an index of refraction. Given the direction of the incident beam at the interface of vacuum and the material, the direction of the outgoing beam can be determined using Snell’s formula. All naturally available materials possess a positive refractive index. In lefthanded materials EM waves bend negatively and consequently a negative index of refractive index can be assigned to such materials without violating Maxwell’s equations. This negative bending allows considerable control over light propagation and opens the door for new approaches to a variety of applications from microwave to optical frequencies. We have demonstrated neagative refraction by a metallic photonic crystal.

},

keywords = {},

pubstate = {published},

tppubtype = {incollection}

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Lu, Wentao; Sridhar, Srinivas

Determination of Refractive Indices of Photonic Crystals: Theory and Experiments Inproceedings

In: APS Meeting Abstracts, 2006.

@inproceedings{lu2006determination,

title = {Determination of Refractive Indices of Photonic Crystals: Theory and Experiments},

author = {Wentao Lu and Srinivas Sridhar},

year = {2006},

date = {2006-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We develop a method to calculate the refractive indices of photonic crystal based on plane wave expansion. The appearance of surface waves and subwavelength imaging is explained within this frame. Numerical simulations of 1D and 2D crystals are performed to support our theory. Comparisons are presented with experimental results on microwave photonic crystals.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

Nagesha, Dattatri; Amiji, Mansoor M; Sridhar, Srinivas

Surface-Engineered Nanomaterials for Nanomedicine Inproceedings

In: ASME 2006 International Manufacturing Science and Engineering Conference, pp. 363–372, American Society of Mechanical Engineers Digital Collection 2006.

@inproceedings{nagesha2006surface,

title = {Surface-Engineered Nanomaterials for Nanomedicine},

author = {Dattatri Nagesha and Mansoor M Amiji and Srinivas Sridhar},

year = {2006},

date = {2006-01-01},

booktitle = {ASME 2006 International Manufacturing Science and Engineering Conference},

pages = {363--372},

organization = {American Society of Mechanical Engineers Digital Collection},

abstract = {An important feature of nanoparticles is the increased ratio of surface area to volume resulting in large percentage of the atoms on the surface, making them very reactive and offers opportunities to manipulate the properties through these surface atoms. For the most efficient use of nanoparticles in various applications, including biology and medicine, it is important to be able to manipulate the surface chemistry. This paper describes the synthesis and characterization of nanoparticles and the various surface engineering techniques that are utilized for optimizing their applications in nanomedicine.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

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Vodo, P; Lu, WT; Huang, Y; Sridhar, S

Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals Journal Article

In: Applied physics letters, vol. 89, no. 8, pp. 084104, 2006.

@article{vodo2006negative,

title = {Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals},

author = {P Vodo and WT Lu and Y Huang and S Sridhar},

year = {2006},

date = {2006-01-01},

journal = {Applied physics letters},

volume = {89},

number = {8},

pages = {084104},

publisher = {American Institute of Physics},

abstract = {Negative refraction is demonstrated in one-dimensional _1D_ dielectric photonic crystals _PCs_ at microwave frequencies. Focusing by plano-concave lens made of 1D PCs due to negative refraction is also demonstrated. The frequency-dependent negative refractive indices, calculated from the experimental data, match very well with those determined from band structure calculations. The easy fabrication of one-dimensional photonic crystals may open the door for future applications.

},

keywords = {},

pubstate = {published},

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### 2004

Gennaro, Emiliano Di; Parimi, Patanjali V; Vodo, Plarenta; Lu, Wentao; Sridhar, Srinivas

Microwave pulse propagation measurements in left-handed materials Inproceedings

In: APS Meeting Abstracts, 2004.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{di2004microwave,

title = {Microwave pulse propagation measurements in left-handed materials},

author = {Emiliano Di Gennaro and Patanjali V Parimi and Plarenta Vodo and Wentao Lu and Srinivas Sridhar},

year = {2004},

date = {2004-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Left handed electromagnetism is well established in media with negative permeability and permittivity and in photonic crystals [1]. In such media the negative refractive index is accompanied by large dispersion dn/dω, and consequently a very low group velocity is predicted for left-handed metamaterial (LHM). It is well known that an artificial material consisting of interleaved arrays of wires and split ring resonators in a certain microwave frequency range shows left handed behavior. We have carried out pulse measurements on LHM using a transition analyzer in order to measure the group velocity. Time delay measurements are performed in an X-band and parallel plate waveguide. Sending a 100ns width pulse with a carrier frequency ranging between 9 and 11 GHz, we analyze the signal delay due to the sample. The results suggest that the group velocity in the LHM is very low. Pulse delay measurements in photonic crystals are also discussed. Work supported by NSF & AFRL [1]. P. V. Parimi et al., submitted (2003).},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

Vodo, P; Parimi, V; Lu, WT; Sridhar, S

Strongly Modulated Photonic Crystal with Tailor Made Negative Refractive Index Technical Report

NORTHEASTERN UNIV BOSTON MA 2004.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@techreport{vodo2004strongly,

title = {Strongly Modulated Photonic Crystal with Tailor Made Negative Refractive Index},

author = {P Vodo and V Parimi and WT Lu and S Sridhar},

year = {2004},

date = {2004-01-01},

institution = {NORTHEASTERN UNIV BOSTON MA},

abstract = {Negative refraction and left-handed electromagnetism in a metallic photonic crystal (PC) wedge are demonstrated in free space for both transverse magnetic and electric mode propagation. The experimental results are in excellent agreement with numerical calculations based on the band structure with no fit parameters used in modeling. The results demonstrate precision control on the design and fabrication of the PC to achieve tailor-made refractive indices between-0.6 to+ 1.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {techreport}

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Sridhar, Srinivas

Imaging by Flat Lens Using Negative Refraction in Microwave Photonic Crystals Inproceedings

In: APS March Meeting Abstracts, 2004.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{sridhar2004imaging,

title = {Imaging by Flat Lens Using Negative Refraction in Microwave Photonic Crystals},

author = {Srinivas Sridhar},

year = {2004},

date = {2004-01-01},

booktitle = {APS March Meeting Abstracts},

abstract = {Metamaterials with negative indices of refraction exhibit novel aspects of electromagnetic wave propagation. Here we report the observation of negative refraction (NR) at microwave frequencies in metallic and dielectric photonic crystal (PC) prisms. The NR observed in the PC corresponds to left-handed electromagnetism and arises due to the dispersion characteristics of waves in a periodic medium. This mechanism for NR is different from that in metamaterials where locally both the dielectric permittivity and magnetic permeability are negative. The PC prism exhibits both positive and negative refraction in different spectral windows, and experimental results are in complete agreement with band-structure calculations and numerical simulations. A remarkable consequence of NR noted by Veselago is that of focusing by a flat lens. We have demonstrated imaging of a microwave point source by a flat lens fabricated from a PC. We also demonstrate a unique feature of a flat lens, the absence of an optical axis, by moving the object and showing that the image displaces correspondingly. The PC flat lens has some interesting similarities and differences compared with the Veselago lens. Potential applications of negative refraction and flat lens imaging at microwave and optical frequencies, including sub-wavelength image resolution suggested by Pendry, will be described. Collaborators: P.Parimi, W.T.Lu, P.Vodo, J.S.Derov. Supported by National Science Foundation and the Air Force Research Laboratories, Hanscom. 1. "Imaging by flat lens using negative refraction", P.Parimi, W.T.Lu, P.Vodo and S.Sridhar, Nature, v.426, 404 (2003). 2. "Negative refraction and left-handed electromagnetism in metallic microwave photonic crystals", P. Parimi, W.T. Lu, P. Vodo, J. Sokoloff, J.S.Derov and S. Sridhar, cond-mat/0306109.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

### 2003

Parimi, Patanjali V; Lu, Wentao T; Vodo, Plarenta; Sridhar, Srinivas

Imaging by flat lens using negative refraction Journal Article

In: Nature, vol. 426, no. 6965, pp. 404–404, 2003.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@article{parimi2003imaging,

title = {Imaging by flat lens using negative refraction},

author = {Patanjali V Parimi and Wentao T Lu and Plarenta Vodo and Srinivas Sridhar},

year = {2003},

date = {2003-01-01},

journal = {Nature},

volume = {426},

number = {6965},

pages = {404--404},

publisher = {Nature Publishing Group},

abstract = {Metamaterials with negative indices of refraction exhibit novel aspects of electromagnetic wave propagation. Here we report the observation of negative refraction (NR) at microwave frequencies in metallic and dielectric photonic crystal (PC) prisms. The NR observed in the PC corresponds to left-handed electromagnetism and arises due to the dispersion characteristics of waves in a periodic medium. This mechanism for NR is different from that in metamaterials where locally both the dielectric permittivity and magnetic permeability are negative. The PC prism exhibits both positive and negative refraction in different spectral windows, and experimental results are in complete agreement with band-structure calculations and numerical simulations. A remarkable consequence of NR noted by Veselago is that of focusing by a flat lens. We have demonstrated imaging of a microwave point source by a flat lens fabricated from a PC. We also demonstrate a unique feature of a flat lens, the absence of an optical axis, by moving the object and showing that the image displaces correspondingly. The PC flat lens has some interesting similarities and differences compared with the Veselago lens. Potential applications of negative refraction and flat lens imaging at microwave and optical frequencies, including sub-wavelength image resolution suggested by Pendry, will be described. Collaborators: P.Parimi, W.T.Lu, P.Vodo, J.S.Derov. Supported by National Science Foundation and the Air Force Research Laboratories, Hanscom. 1. "Imaging by flat lens using negative refraction", P.Parimi, W.T.Lu, P.Vodo and S.Sridhar, Nature, v.426, 404 (2003). 2. "Negative refraction and left-handed electromagnetism in metallic microwave photonic crystals", P. Parimi, W.T. Lu, P. Vodo, J. Sokoloff, J.S.Derov and S. Sridhar, cond-mat/0306109.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

Lu, WT; Sokoloff, JB; Sridhar, S

Inproceedings

In: APS Meeting Abstracts, 2003.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{lu2003perfect,

author = {WT Lu and JB Sokoloff and S Sridhar},

year = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We study analytically and numerically imaging by Â" perfect lensÂ" made of negative index medium (NIM)(or left-handed meta-material (LHM)). For far field, the perfect lens is only perfect for n=-1. Away from this value, aberration and caustics will be present. For near field imaging with Re ε=-1, the consequences of departure from dielectric matching and losses are discussed. Work supported by NSF-0098801 and AFRL, Hanscom.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

Lu, WT; Sridhar, S

Near-field imaging by negative permittivity media Journal Article

In: Microwave and Optical Technology Letters, vol. 39, no. 4, pp. 282–286, 2003.

BibTeX | Tags: Metamaterials and Nanophotonics

@article{lu2003near,

title = {Near-field imaging by negative permittivity media},

author = {WT Lu and S Sridhar},

year = {2003},

date = {2003-01-01},

journal = {Microwave and Optical Technology Letters},

volume = {39},

number = {4},

pages = {282--286},

publisher = {Wiley Online Library},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

Sokoloff, JB; Lu, WT; Sridhar, S

Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium: Always Negative Inproceedings

In: APS Meeting Abstracts, 2003.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{sokoloff2003refraction,

title = {Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium: Always Negative},

author = {JB Sokoloff and WT Lu and S Sridhar},

year = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Since all physical radiation sources admit their radiation in the form of wave packets, we analyze refraction of electromagnetic wave packets on passing from an isotropic positive (PIM) to an isotropic negative index medium (NIM). We definitively show that in all cases the energy is always refracted negatively. For localized waves, the group refraction is always negative. We accomplish this by treating comprehensively group refraction at a PIM-NIM interface by analytical and numerical treatment of several exhaustive examples: localized wave packets, beams, and also a finite number of plane waves. We focus on physically important quantities such as the energy flow and momentum. In all of the cases we show that the energy and momentum refract negatively. We show that in all cases where the wave group does not extend to infinity in the perpendicular direction of the wave vector, the interference pattern also refracts negatively. Work supported by NSF-0098801 and AFRL, Hanscom.

},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

Parimi, Patanjali; Vodo, Plarenta; Lu, Wentao; Sridhar, Srinivas

Microwave Propagation in Negative Index and Artificial Dielectric Media Inproceedings

In: APS Meeting Abstracts, 2003.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{parimi2003microwave,

title = {Microwave Propagation in Negative Index and Artificial Dielectric Media},

author = {Patanjali Parimi and Plarenta Vodo and Wentao Lu and Srinivas Sridhar},

year = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Negative index media (NIM) are fabricated by interleaving arrays of split ring resonators and wire strips. Microwave (X-band) waveguide measurements on the NIM yield quantitative information on the material parameters, % tilden(ω)=n^' +in^' ', tildevarepsilon% (ω )=varepsilon ^' +ivarepsilon ^' ' and tilde% μ(ω )=μ ^' +iμ ^' ' . Typical NIM features such as passband in the NIM region expected from the theoretical analysis are observed in the measured data. The n^'(ω) determined from the waveguide transmission parameters (tildeS_11,tildeS_21) is found to vary from -4.8 to-0.3 in the passband region 9.6-10.5GHz. The results show that transmission is optimized for n^' (ω ) -1 and low n^' ' . A detailed investigation of several NIM materials suggests that the characteristic properties of the NIM are dependent on the length of the material, choice of the substrate material, and continuity in the wire strips. Artificial dielectric media fabricated with arrays of wire strips exhibit a characteristic microwave plasmon mode in the X-band region, below which varepsilon ^' (ω )<0. Work supported by the National Science Foundation and the Air Force Research Labs, Hanscom.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

### 2002

Kaso, A; Parimi, PV; Sridhar, S; Derov, JS

Microwave Transmission in Left-Handed Metamaterials Inproceedings

In: APS Meeting Abstracts, 2002.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@inproceedings{kaso2002microwave,

title = {Microwave Transmission in Left-Handed Metamaterials},

author = {A Kaso and PV Parimi and S Sridhar and JS Derov},

year = {2002},

date = {2002-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {As has been already shown, a material with both ε and mu negative can sustain propagation waves. The permittivity ε and permeability mu should necessarily be frequency dependent for the causality principle to hold. We consider the dispersive expressions obtained by theoretical considerations from JB Pendry. We try to obtain some useful insight for pulse propagation, like group velocity v_g, the spreading of the wave packet in time in the disperssive medium. Transmission and reflectivity are computed for a normal incidence of the pulse on the slab. All the above situations can prove useful in the applications of this new metamaterial, such as in the delay lines where high values of the index of refraction are needed. particular attention is given to the frequency range where the material displays n=-1. Experiments are underway exploring the properties of LHM and the results will be discussed.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {inproceedings}

}

Lu, WT; Sokoloff, JB; Sridhar, S

Comment on Journal Article

In: arXiv preprint cond-mat/0207689, 2002.

Abstract | BibTeX | Tags: Metamaterials and Nanophotonics

@article{lu2002comment,

title = {Comment on},

author = {WT Lu and JB Sokoloff and S Sridhar},

year = {2002},

date = {2002-01-01},

journal = {arXiv preprint cond-mat/0207689},

abstract = {Valanju, Walser and Valanju (VWV) [1] have shown

that for a group consisting of two plane waves incident

on the interface between a material of positive refractive

index (PIM) and material of negative refractive index

(NIM), the group velocity refracts positively. Here we

show that this is true only for the special two plane wave

case constructed by VWV, but for generic localized wave

packets, the group refraction is generically negative.

The sum of two plane waves of wavevector and frequency (k1, ω1) and (k2, ω2), considered by VWV, can

be written as 2e

i(k0·r−ω0t)

cos[(1/2)(∆k · r − ∆ωt)],

where (k0, ω0) the average wavevector and frequency and

(∆k, ∆ω) denote their differences. Clearly, the argument

of the cosine is constant along planes, which propagate

in time along the direction of their normal, ∆k. We

have carried out numerical simulations of wave packets

incident on the PIM-NIM interface and for the 2-wave

case arrive at conclusions similar to VWV. For arbitrary

number of incident plane waves whose k vectors are all

parallel, the group refraction is again positive. Note that

in all these special cases the packet remains nonzero on

infinite planes.

Here we show that for any wave packet that is spatially

localized, the group refraction is generically negative.

For 3 (or more) waves whose wave vectors not aligned,

the group refraction will be negative. For example, consider three wave vectors in PIM in the x-z-plane, whose

magnitudes are, k − δk, k, k − δk and whose angles with

the z-axis are, θ − δθ, θ, θ + δθ, respectively. The dispersion k

2 = (ω

2 − ω

2

p

)(ω

2 − ω

2

b

)/c2

(ω

2 − ω

2

0

) were used for

NIM. The results are shown in Fig. 1. The wave packet

refracts negatively, in obvious contrast to VWV. As we

have seen, two plane waves result in a wave packet-like

structure which is constant along planes; the addition of

a third wave breaks the planes into localized wave packets

which refract negatively.

A packet constructed from a finite number of plane

waves will always give a collection of propagating wave

pulses, as seen in Fig. 1. A wave packet localized in one

region of space, as occurs in all experimental situations,

can only be constructed from a continuous distribution of

wavevectors. Consider such a wave packet incident from

outside the NIM, E = E0

R

d

2kf(k − k0)e

i(k·r−ω(k)t)

,

where ω(k) = ck. If f(k − k0) drops off rapidly as k

moves away from k0, ω(k) can be expanded in a Taylor

series to first order in k − k0 to a good approximation.

This gives, E = E0e

i(k0·r−ω(k0)t

g(r − ctk0/k0), where

g(R) = R

d

2kf(k−k0)e

i(k−k0)·R. Inside the NIM, k and

k0 in the argument of the exponent get replaced by kr

and kr0 which are related to k and k0 by Snell’s law.

Then the wave packet once it enters the NIM is given by

Er = E

′

0

e

i(kr0·r−ω(kr0)t

gr(r − vgrt), (1)

where gr(R) = R

d

2kf(k − k0)e

iR·[(k−k0)·∇kkr]

. Here

kr0 denotes kr evaluated at k = k0 and vgr = ∇kr ω(kr)

evaluated at kr = kr0. Thus, the refracted wave moves

with the group velocity vgr. Evaluation of Eq. (1) for

a Gaussian wave packet shows that the incident packet

gets distorted but the maximum of the packet moves at

vgr. For the case of an isotropic medium, considered by

VWV [1], the group velocity is anti-parallel to the wave

vector in the medium. Hence, the group velocity will be

refracted the same way as the wavevector is, contrary to

the claim of VWV [1].

Thus VWV’s statement that the “Group Refraction is

always positive” is true only for the very special (and

rare) wave packets constructed by them and is incorrect

for more general wave packets that are spatially localized.

This work was supported by the National Science

Foundation, the Air Force Research Laboratories and the

Department of Energy.

W. T. Lu, J. B. Sokoloff and S. Sridhar

Department of Physics, Northeastern University, 360

Huntington Avenue, Boston, MA 02115.},

keywords = {Metamaterials and Nanophotonics},

pubstate = {published},

tppubtype = {article}

}

that for a group consisting of two plane waves incident

on the interface between a material of positive refractive

index (PIM) and material of negative refractive index

(NIM), the group velocity refracts positively. Here we

show that this is true only for the special two plane wave

case constructed by VWV, but for generic localized wave

packets, the group refraction is generically negative.

The sum of two plane waves of wavevector and frequency (k1, ω1) and (k2, ω2), considered by VWV, can

be written as 2e

i(k0·r−ω0t)

cos[(1/2)(∆k · r − ∆ωt)],

where (k0, ω0) the average wavevector and frequency and

(∆k, ∆ω) denote their differences. Clearly, the argument

of the cosine is constant along planes, which propagate

in time along the direction of their normal, ∆k. We

have carried out numerical simulations of wave packets

incident on the PIM-NIM interface and for the 2-wave

case arrive at conclusions similar to VWV. For arbitrary

number of incident plane waves whose k vectors are all

parallel, the group refraction is again positive. Note that

in all these special cases the packet remains nonzero on

infinite planes.

Here we show that for any wave packet that is spatially

localized, the group refraction is generically negative.

For 3 (or more) waves whose wave vectors not aligned,

the group refraction will be negative. For example, consider three wave vectors in PIM in the x-z-plane, whose

magnitudes are, k − δk, k, k − δk and whose angles with

the z-axis are, θ − δθ, θ, θ + δθ, respectively. The dispersion k

2 = (ω

2 − ω

2

p

)(ω

2 − ω

2

b

)/c2

(ω

2 − ω

2

0

) were used for

NIM. The results are shown in Fig. 1. The wave packet

refracts negatively, in obvious contrast to VWV. As we

have seen, two plane waves result in a wave packet-like

structure which is constant along planes; the addition of

a third wave breaks the planes into localized wave packets

which refract negatively.

A packet constructed from a finite number of plane

waves will always give a collection of propagating wave

pulses, as seen in Fig. 1. A wave packet localized in one

region of space, as occurs in all experimental situations,

can only be constructed from a continuous distribution of

wavevectors. Consider such a wave packet incident from

outside the NIM, E = E0

R

d

2kf(k − k0)e

i(k·r−ω(k)t)

,

where ω(k) = ck. If f(k − k0) drops off rapidly as k

moves away from k0, ω(k) can be expanded in a Taylor

series to first order in k − k0 to a good approximation.

This gives, E = E0e

i(k0·r−ω(k0)t

g(r − ctk0/k0), where

g(R) = R

d

2kf(k−k0)e

i(k−k0)·R. Inside the NIM, k and

k0 in the argument of the exponent get replaced by kr

and kr0 which are related to k and k0 by Snell’s law.

Then the wave packet once it enters the NIM is given by

Er = E

′

0

e

i(kr0·r−ω(kr0)t

gr(r − vgrt), (1)

where gr(R) = R

d

2kf(k − k0)e

iR·[(k−k0)·∇kkr]

. Here

kr0 denotes kr evaluated at k = k0 and vgr = ∇kr ω(kr)

evaluated at kr = kr0. Thus, the refracted wave moves

with the group velocity vgr. Evaluation of Eq. (1) for

a Gaussian wave packet shows that the incident packet

gets distorted but the maximum of the packet moves at

vgr. For the case of an isotropic medium, considered by

VWV [1], the group velocity is anti-parallel to the wave

vector in the medium. Hence, the group velocity will be

refracted the same way as the wavevector is, contrary to

the claim of VWV [1].

Thus VWV’s statement that the “Group Refraction is

always positive” is true only for the very special (and

rare) wave packets constructed by them and is incorrect

for more general wave packets that are spatially localized.

This work was supported by the National Science

Foundation, the Air Force Research Laboratories and the

Department of Energy.

W. T. Lu, J. B. Sokoloff and S. Sridhar

Department of Physics, Northeastern University, 360

Huntington Avenue, Boston, MA 02115.